JP2004183612A - Valve drive system and valve drive device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve drive system capable of efficiently opening and closing an intake valve or a discharge valve of an internal combustion engine having a plurality of cylinders by a motor. <P>SOLUTION: This valve drive system 10 applied to an internal combustion engine 1 having a plurality of cylinders 2 drives an intake valve 4 or a discharge valve 5 installed to each of the cylinders 2. The valve drive system 10 is installed in a manner to drive the intake valve 4 or the discharge valve 5 of different cylinders 2 of the internal combustion engine 1 respectively, and further comprises a plurality of valve drive devices 11A, 11B having an electric motor 12 as a drive source generating a rotary movement, and a power transmitting mechanism 13 converting and transmitting a rotary movement of the electric motor 12 into a opening/closing movement of drive object valves 4, 5 respectively; and a motor controlling device 40 controlling an action of the electric motor 12 of a plurality of the valve drive devices according to an operating condition of the internal combustion engine 1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a valve drive system that drives an intake valve or an exhaust valve of an internal combustion engine and a valve drive device that forms the system.
[0002]
[Prior art]
An intake valve and an exhaust valve of a general internal combustion engine are opened and closed by power taken from a crankshaft of the internal combustion engine. However, recently, an attempt has been made to drive an intake valve and an exhaust valve by an electric motor. For example, Patent Literature 1 discloses a valve driving device that drives a cam shaft by a motor to open and close an intake valve. Further, although the present invention is directed to a valve for EGR, a valve driving device that converts the rotation of a motor into a linear opening / closing motion of a valve by using a screw mechanism provided on a valve stem is also known (Japanese Patent Application Laid-Open No. H11-157572). Reference 2).
[0003]
[Patent Document 1]
JP-A-8-177536
[Patent Document 2]
JP-A-10-73178
[0004]
[Problems to be solved by the invention]
The device that converts the rotation of the motor into the opening and closing movement of the valve by a screw mechanism requires a large amount of rotation of the motor required to open and close the valve and is inefficient, so the valve needs to operate the valve at high speed and periodically. It is not suitable as a driving device for a valve or an exhaust valve.
[0005]
On the other hand, when the camshaft is rotated by a motor, the intake valve and the exhaust valve can be efficiently driven. However, in a multi-cylinder internal combustion engine generally used as a power source of a vehicle, a camshaft is shared between a plurality of cylinders arranged in a line. By simply driving such a shared camshaft with a motor, a change in the operation of the camshaft affects the operating characteristics of all intake and exhaust valves driven by the camshaft. Therefore, the degree of freedom of the operating characteristics obtained by controlling the motor is not so high.
[0006]
Therefore, the present invention provides an internal combustion engine that can efficiently open and close an intake valve or an exhaust valve of an internal combustion engine having a plurality of cylinders with a motor, and can increase the degree of freedom regarding the operating characteristics of each valve as compared with the related art. It is an object of the present invention to provide a valve drive system of an engine and a valve drive used in the system.
[0007]
[Means for Solving the Problems]
The valve drive system of the present invention is applied to an internal combustion engine having a plurality of cylinders, and is a valve drive system of an internal combustion engine for driving intake or exhaust valves provided in each cylinder, wherein the internal combustion engine An electric motor as a drive source for generating a rotational motion, and a power transmission for converting the rotational motion of the electric motor into an opening and closing motion of a valve to be driven and transmitting the electric power. A plurality of valve drive devices each including a mechanism, and motor control means for controlling the operation of the electric motor of each of the plurality of valve drive devices according to the operation state of the internal combustion engine, the above-described configuration is provided. The problem is solved (claim 1).
[0008]
According to the valve drive system of the present invention, by providing the plurality of valve drive devices, it is possible to provide each of the intake valves or the exhaust valves of the plurality of cylinders with appropriate operation characteristics according to the operation state of the internal combustion engine. Can be. In the valve drive system of the present invention, each of the plurality of valve drive devices may drive the intake valve or the exhaust valve of a different cylinder. Therefore, the valve drive device may be provided independently for each cylinder, or a valve drive device may be provided independently for the intake valve and the exhaust valve of each cylinder. On the other hand, some or all of the valve driving devices may drive the intake valves or exhaust valves of two or more different cylinders. In particular, if the intake valve is open or the exhaust valve is open between cylinders that do not overlap, even if the intake valve or exhaust valve of those cylinders is driven by a common electric motor, each cylinder Can be changed without being influenced by the operation of the intake valve or the exhaust valve driven by the common electric motor.
[0009]
In the valve drive system according to the aspect of the invention, the motor control unit controls the operation of the electric motor such that at least one operating characteristic of a valve operating angle, a lift characteristic, or a maximum lift amount of the valve to be driven changes. The control can be performed according to the operating state of the internal combustion engine (claim 2). In this case, the operation of the intake valve and the exhaust valve can be changed more flexibly than in a conventional valve drive device that changes only the opening / closing timing. If the rotational speed of the electric motor is increased or decreased while the intake valve or the exhaust valve is open, the operating angle changes, and if the rotational speed changes, that is, if the acceleration is changed, the lift characteristics change. The lift characteristics are grasped as characteristics relating to the correspondence between the lift amount of the intake valve or the exhaust valve and the crank angle. Regarding the lift amount, the intake valve or the exhaust valve is controlled by switching the rotation direction of the cam so as to reverse the cam earlier than reaching the maximum lift position where the lift amount of the intake valve or the exhaust valve is maximized. Can be limited to be smaller than the maximum lift amount.
[0010]
In the valve drive system of the present invention, the power transmission mechanism can convert the rotational motion of the electric motor into the opening and closing motion of the intake valve and the exhaust valve by using a cam and a link. If the rotational motion of the motor is converted into the opening and closing motion of the intake and exhaust valves via cams and links, the ratio of the momentum of the valve to the rotation of the motor can be increased compared to the case where a screw mechanism is used. . In other words, in the case of the screw mechanism, the valve cannot be opened and closed sufficiently without turning the screw at least a few turns.However, in the case of using a cam or link, one rotation of the motor completes one cycle of movement. In addition, a predetermined opening / closing operation can be applied to the intake valve and the exhaust valve only by rotating the motor at most once. Therefore, the intake valve or the exhaust valve can be efficiently driven.
[0011]
A valve drive system that converts rotation of an electric motor into opening and closing motion of an intake valve or an exhaust valve by a cam (claim 3) can further include the following aspects.
[0012]
The motor control means may set a control amount of the electric motor in consideration of a change in friction torque acting on rotation of the cam (claim 4). When the operation of the electric motor is controlled without considering the cam friction torque, the rotation speed of the motor fluctuates from the control target value due to the influence of the cam friction torque, so that the operation characteristics of the intake valve or the exhaust valve are controlled. The deviation from the target affects the operating state of the internal combustion engine 1. For example, fuel efficiency may deteriorate, performance may deteriorate, exhaust emission may deteriorate, and the like. Control of the electric motor may be unstable. These disadvantages can be solved by adjusting the control amount of the electric motor in consideration of the cam friction torque. In the present invention, the friction torque means a rotation resistance applied to a driving source of a cam based on a mechanical configuration from an electric motor to an intake valve or an exhaust valve. The frictional force generated in the mechanism from the drive source to the intake valve or the exhaust valve increases the friction torque in the positive direction, and the repulsive force of the spring means (valve spring) that pushes the intake valve and the exhaust valve back in the closing direction is Increase the friction torque in the negative direction. When controlling the electric motor, it is necessary to output the torque required to rotate the cam against the friction torque, and the control of the electric motor is realized by increasing or decreasing a control variable (parameter) associated with the output torque. Is done. The setting and adjustment of the control amount of the electric motor in the present invention means the setting and adjustment of such control variables.
[0013]
The motor control means may set the control amount of the electric motor in consideration of a control state regarding characteristics of intake or exhaust of the internal combustion engine (claim 5). If the operation of the intake valve or the exhaust valve deviates from the target of the control, the intake characteristics and the exhaust characteristics of the internal combustion engine cannot be controlled as intended, resulting in inconveniences such as deterioration of fuel consumption, performance degradation, and reduction of exhaust emission. On the other hand, by taking into account the control state related to the characteristics of intake or exhaust, and adjusting the control amount of the electric motor to reduce the deviation if the control state deviates from the target, such a disadvantage can be solved. Can be.
[0014]
Various states that correlate with the operating characteristics of the intake or exhaust valve may be considered as the characteristics of the intake or exhaust. For example, the in-cylinder intake air amount, the in-cylinder pressure, the internal EGR amount, the exhaust temperature, the air-fuel ratio, and the like may be considered as characteristics of intake or exhaust. When the control state of the air-fuel ratio is considered, it is preferable that the motor control means corrects the control amount of the motor so that the air-fuel ratio is controlled to a predetermined target value. By performing such control, the deviation of the air-fuel ratio can be eliminated by correcting the operation characteristics of the intake valve or the exhaust valve, and good results such as improved fuel efficiency, increased output, and improved exhaust emission can be obtained.
[0015]
Further, in the valve drive system, an abnormality that determines the presence or absence of an abnormality in the valve drive system based on a correction amount with respect to the control amount of the electric motor given by considering a control state regarding intake or exhaust characteristics of the internal combustion engine. A determination means may be provided (claim 7). If any abnormality occurs in the valve drive system, the absolute value of the control amount of the electric motor becomes too large or too small, or the amount of change in the control amount becomes excessive. Therefore, by monitoring the correction amount related to the control amount of the electric motor, it is possible to determine whether or not an abnormality has occurred in the valve drive system without using a sensor for detecting abnormality.
[0016]
The motor control means may predict a change in the number of revolutions of the internal combustion engine based on a change in an operation state of the internal combustion engine, and may set a control amount of the electric motor in consideration of the prediction result. Item 8). In this case, when the rotational speed of the internal combustion engine suddenly changes, the control amount of the electric motor is increased / decreased in anticipation of the change, so that the response of the rotational speed of the cam to the change in the rotational speed of the internal combustion engine is obtained. Can be enhanced.
[0017]
When the friction torque of the cam becomes a negative value, the electric motor may be driven by the rotational movement of the cam to generate electric power by the electric motor. In this case, the efficiency of the valve drive system can be increased, the capacity of the battery required for driving the cam can be reduced, and the power generation capacity of the alternator mounted as a generator in the vehicle can be set smaller.
[0018]
Motor rotation position detection means for detecting a rotation position of the electric motor is attached to the electric motor, and the motor control means determines a rotation position of the cam based on a detection result of the rotation position of the electric motor. It may be provided with a specifying means (claim 10). By estimating the cam position from the rotation position of the motor, it is not necessary to provide a separate sensor for detecting the cam position.
[0019]
When the reduction ratio between the electric motor and the cam is N: M (where N> M, and N and M are integers having no common divisor other than 1, N is set to 6 or less. It is desirable (claim 11). With such a setting, the initial position of the cam can be easily detected, and the detection error can be suppressed.
[0020]
The motor control means rotates the electric motor according to predetermined conditions when the internal combustion engine is in a predetermined state, and drives the electric motor which appears during the rotation in correlation with a change in friction torque of the cam. An initialization means for grasping the rotation position of the cam based on a change in the state may be provided (claim 12). The friction torque of the cam correlates with the opening / closing state of the intake valve or the exhaust valve by the cam, and generally, the friction torque reverses near the cam position where the lift amount of the intake valve or the exhaust valve is maximized. On the other hand, the friction torque affects the driving state of the electric motor. For example, if the output torque of the electric motor is kept constant, the rotation speed of the motor decreases as the friction torque increases, and the rotation speed of the motor increases as the friction torque decreases. If the rotational speed of the electric motor is kept constant, the output torque of the motor increases as the friction torque increases, and the output torque of the motor decreases as the friction torque decreases. By utilizing such a correlation, the position of the cam can be specified only by monitoring the driving state of the motor. Utilizing the fact that a change in the number of revolutions or a change in the output torque of the electric motor at the start of opening or closing of the intake valve or exhaust valve is in a predetermined state, the position of the cam is determined when such a change occurs. May be specified. In this case, the driving power required to specify the position of the cam can be reduced. Further, when the operation is performed when the internal combustion engine is stopped, interference between the intake valve or the exhaust valve and the piston can be avoided.
[0021]
The initialization means is configured to rotate the electric motor when the internal combustion engine is stopped to determine the rotational position of the cam, and to store information indicating the determined rotational position of the cam even during the stop period of the internal combustion engine. The motor control means specifies the rotational position of the cam based on the information stored in the storage device and starts control of the electric motor at the next start of the internal combustion engine. (Claim 13). In this case, it is not necessary to perform the processing by the initialization means in order to grasp the rotational position of the cam when starting the internal combustion engine. Therefore, a quick start of the internal combustion engine becomes possible.
[0022]
The motor control unit may include a valve rotation execution unit that drives the electric motor such that the valve rotates around its axis at a predetermined time during the stop of the internal combustion engine (claim 14). In this case, by rotating the valve, carbon attached to the valve and its seat (valve seat) can be scraped off. The position of contact of the valve with a drive member such as a rocker arm can be changed around the axis of the valve to prevent uneven wear of the valve.
[0023]
The motor control means controls the amount of lift of the electric motor so that the amount of lift of the valve is limited to a predetermined value smaller than the maximum amount of lift obtained when the cam is rotated once. Means may be provided (claim 15). In this case, by rotating the cam forward and backward, the lift amount can be limited to be smaller than the maximum lift amount that can be given to the intake valve or the exhaust valve by the cam, and the intake valve or the exhaust valve can be opened and closed. Therefore, even if the cam is designed in accordance with the intake air amount at the time of high rotation and high load, it is possible to cope with the operation state of low rotation and low load where the intake air amount is small. The rotation angle when rotating the cam in the normal or reverse direction may be increased or decreased according to the lift amount to be given to the intake valve or the exhaust valve.
[0024]
The motor control means, the drive mode of the electric motor according to the operating state of the internal combustion engine, a forward rotation mode to drive the electric motor only in the forward direction, and a forward and reverse rotation mode to rotate the electric motor forward and reverse Mode switching means for switching between the two modes (claim 16). In this case, the cam is rotated forward and reverse at low rotation and low load to limit the lift amount, and at high rotation and high load, the cam is rotated forward and the cam is rotated at high speed and with small torque by the inertia of the camshaft or the like. The driving state of the cam can be properly used.
[0025]
The valve drive device according to the present invention includes an electric motor as a drive source that generates a rotational motion, a power transmission mechanism that converts the rotational motion of the electric motor into an opening and closing motion of a valve to be driven and transmits the same, and an operation of the internal combustion engine. Motor control means for controlling the operation of the electric motor such that at least one operating characteristic of the valve operating angle, lift characteristic, or maximum lift amount of the valve to be driven changes according to a state. The above-mentioned problem is solved (claim 17). According to such a valve drive device, by controlling the operation of the electric motor, it is possible to change at least one of the operating angle of the intake valve or the exhaust valve, the lift characteristic, or the maximum lift amount. The operation of the intake valve and the exhaust valve can be changed more flexibly as compared with a conventional valve drive device that changes the operation. In addition, the valve drive device of the present invention may include various preferable aspects of the above-described valve drive system using a cam.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
[0027]
FIG. 1 shows an internal combustion engine 1 in which a valve drive system according to a first embodiment of the present invention is incorporated. The internal combustion engine 1 is configured as a multi-cylinder in-line gasoline engine in which a plurality of (four in the figure) cylinders (cylinders) 2... 2 are arranged in one direction, and a piston 3 is mounted on each cylinder 2 so as to be vertically movable. ing. Above each cylinder 2, two intake valves 4 and two exhaust valves 5 are provided, respectively. The intake valve 4 and the exhaust valve 5 are linked with the up and down movement of the piston 3 so that a valve drive system 10 is provided. , The intake air to the cylinder 2 and the exhaust air from the cylinder 2 are performed.
[0028]
The valve drive system 10 includes valve drive devices 11A... 11A provided one by one on the intake side of each cylinder 2 and valve drive devices 11B... 11B provided one by one on the exhaust side of each cylinder 2. I have. Each of these valve driving devices 11A and 11B drives the intake valve 4 or the exhaust valve 5 using a cam. The configurations of the valve driving devices 11A are equal to each other, and the configurations of the valve driving devices 11B are equal to each other. FIG. 2 shows intake and exhaust valve drive devices 11A and 11B provided in association with one cylinder 2. Note that the valve driving devices 11A and 11B have a similar configuration to each other, and the valve driving device 11A on the intake side will be described first.
[0029]
The intake-side valve driving device 11A includes an electric motor (hereinafter, may be abbreviated as a motor) 12 as a driving source, and power transmission for converting a rotational movement of the motor 12 into a linear opening and closing movement of the intake valve 4. And a mechanism 13. As the motor 12, a DC brushless motor or the like whose rotation speed can be controlled is used. The motor 12 has built-in rotational position detecting means such as a resolver and a rotary encoder for detecting the rotational position.
[0030]
The power transmission mechanism 13 includes a single camshaft 14A, a gear train 15 for transmitting the rotational motion of the motor 12 to the camshaft 14A, a rocker arm 16 for driving the intake valve 4, a camshaft 14A and the rocker arm 16. And a valve characteristic adjusting mechanism 17 interposed therebetween. The camshaft 14A is provided independently for each cylinder 2. In other words, the camshaft 14A is divided for each cylinder 2. The gear train 15 synchronizes with the motor 12 by transmitting the rotation of a motor gear 18 attached to an output shaft (not shown) of the motor 12 to a cam drive gear 20 integrated with the cam shaft 14A via an intermediate gear 19. To rotate the camshaft 14A.
[0031]
As shown in FIGS. 3 and 4, a single cam 21A is provided on the cam shaft 14A so as to be integrally rotatable. The cam 21A is formed as a kind of a plate cam obtained by expanding a part of a base circle coaxial with the cam shaft 14A. The profiles (outer peripheral contours) of the cams 21A are equal among all the valve driving devices 11A. The profile of the cam 21A is set so that a negative curvature does not occur over the entire circumference, that is, such that the cam 21A draws a convex curved surface outward in the radial direction.
[0032]
The rocker arm 16 is provided so as to be swingable about a support shaft 22. The intake valve 4 is urged toward the rocker arm 16 by a valve spring 23, whereby the intake valve 4 comes into close contact with a valve seat (not shown) of the intake port, and the intake port is closed. The other end of the rocker arm 16 is in contact with the adjuster 24. When the adjuster 24 pushes up the other end of the rocker arm 16, the rocker arm 16 is kept in a state where one end of the rocker arm 16 is in contact with the upper end of the intake valve 4.
[0033]
The valve characteristic adjusting mechanism 17 functions as an intermediary for transmitting the rotational movement of the cam 21A to the rocker arm 16 as a rocking movement, and changes the correlation between the rotational movement of the cam 21A and the rocking movement of the rocker arm 16. This also functions as a lift amount and operating angle changing means for changing the lift amount and operating angle of the intake valve 4.
[0034]
As shown in FIG. 5, the valve characteristic adjustment mechanism 17 includes a support shaft 30, an operation shaft 31 disposed through the center of the support shaft 30, and a first ring 32 disposed on the support shaft 30. , And two second rings 33, 33 arranged on both sides thereof. The support shaft 30 is fixedly attached to a cylinder head or the like of the internal combustion engine 1. The operation shaft 31 is reciprocated in the axial direction (R direction and F direction in FIG. 6) with respect to the support shaft 30 by an actuator (not shown). The first ring 32 and the second ring 33 are supported slidably in the axial direction and swingable in the circumferential direction with respect to the support shaft 30. A roller follower 34 is rotatably mounted on the outer periphery of the first ring 32, and a nose 35 is formed on the outer periphery of the second ring 33.
[0035]
As shown in FIG. 6, a slider 36 is provided on the outer periphery of the support shaft 30. The slider 36 is slidable in the axial direction integrally with the operation shaft 31 with respect to the support shaft 30 by engaging a long hole 36 c extending in the circumferential direction with a pin 37 attached to the operation shaft 31. The support shaft 30 has an elongated hole (not shown) in the axial direction that allows the pin 37 to move in the axial direction. A first helical spline 36a and second helical splines 36b, 36b arranged so as to sandwich the first helical spline 36a are provided integrally on the outer periphery of the slider 36. The twist direction of the second helical spline 36b is opposite to the twist direction of the first helical spline 36a. On the other hand, a helical spline 32a that meshes with the first helical spline 36a is formed on the inner periphery of the first ring 32, and a helical spline 33a that meshes with the second helical spline 36b is formed on the inner periphery of the second ring 33. I have.
[0036]
As is clear from FIG. 4, the valve characteristic adjusting mechanism 17 is configured such that the roller follower 34 faces the cam 21A and the nose 35 faces one end of the rocker arm 16 corresponding to each intake valve 4, respectively. Attached to. When the roller follower 34 comes into contact with the nose portion 21a and is pushed down with the rotation of the cam 21A, the first ring 32 supporting the roller follower 34 rotates on the support shaft 30 and the rotational movement thereof is performed via the slider 36. The power is transmitted to the second ring 33 and the second ring 33 rotates in the same direction as the first ring 32. Due to the rotation of the second ring 32, the nose 35 pushes down one end of the rocker arm 16, whereby the intake valve 4 is displaced downward against the valve spring 23 and the intake port is opened. When the nose portion 21a gets over the roller follower 34, the intake valve 4 is pushed up by the force of the valve spring 23, and the intake port is closed. Thus, the rotational movement of the camshaft 14A is converted into the opening and closing movement of the intake valve 4.
[0037]
Further, in the valve characteristic adjusting mechanism 17, when the operation shaft 31 is displaced in the axial direction and the slider 36 is slid with respect to the support shaft 30 as shown by arrows R and F in FIG. The second ring 33 rotates in directions opposite to each other in the circumferential direction. When the slider 36 is moved in the direction of arrow F, the first ring 32 rotates in the direction of arrow P, and the second ring 33 rotates in the direction of arrow Q, so that the circumferential distance between the roller follower 34 and the nose 35 increases. . On the other hand, when the slider 36 is moved in the direction of the arrow R, the first ring 32 rotates in the direction of the arrow Q, and the second ring 33 rotates in the direction of the arrow P, so that the circumferential distance between the roller follower 34 and the nose 35 is reduced. Decrease. As the distance between the roller follower 34 and the nose 35 increases, the amount by which the nose 35 pushes down the rocker arm 16 increases, and the lift amount and operating angle of the intake valve 4 also increase. Therefore, the more the operating shaft 31 is operated in the direction of arrow F in FIG. 6, the more the lift amount and the operating angle of the intake valve 4 increase.
[0038]
According to the valve driving device 11A configured as described above, the motor 12 drives the camshaft 14A in one direction at half the rotational speed of the crankshaft of the internal combustion engine 1 (hereinafter referred to as the basic speed). , The intake valve 4 can be opened and closed in synchronization with the rotation of the crankshaft, similarly to a general mechanical valve drive that drives the valve with power from the crankshaft. Further, the lift amount and the operating angle of the intake valve 4 can be changed by the valve characteristic adjusting mechanism 17. Further, according to the valve driving device 11A, by changing the rotation speed of the camshaft 14A by the motor 12 from the basic speed, the relative relationship between the phase of the crankshaft and the phase of the camshaft 14A is changed, so that the intake valve is changed. The operation characteristics (valve opening timing, valve closing timing, lift characteristics, operating angle, and maximum lift amount) of No. 4 can be variously changed.
[0039]
On the other hand, as shown in FIG. 2, in the valve driving device 11B on the exhaust valve 5 side, unlike the valve driving device 11A, two cams 21B are provided on the cam shaft 14B, and the valve characteristic adjusting mechanism 17 is omitted, and The two cams 21B directly drive the rocker arms 16, respectively. Other parts of the valve driving device 11B are common to the valve driving device 11A, and description of those common parts will be omitted. The profile of the cam 21B is formed of a convex curved surface over the entire circumference similarly to the cam 21A. Regarding the exhaust valve 5, the operating characteristics of the exhaust valve 5 can be variously changed by variously changing the driving speed of the cam shaft 14B by the motor 12 of the valve driving device 11B.
[0040]
As shown in FIG. 2, a motor control device 40 is provided in the valve drive system 10 to control the operation characteristics of the motor 12 of the valve drive devices 11A and 11B. The motor control device 40 is configured as a computer having a microprocessor, a RAM as its main storage device, and a ROM, and controls the operation of each electric motor 12 according to a valve control program stored in the ROM. Although FIG. 2 shows the valve driving devices 11A and 11B of one cylinder 2, the motor control device 40 is also used for the valve driving devices 11A and 11B of the other cylinders 2.
[0041]
An A / F sensor 41 that outputs a signal corresponding to an air-fuel ratio of exhaust gas and an opening degree of a throttle valve that adjusts an intake air amount are provided to the motor control device 40 as input means of information necessary for controlling the electric motor 12. , An throttle opening sensor 43 that outputs a signal corresponding to the opening of the accelerator pedal, an air flow meter 44 that outputs a signal corresponding to the amount of intake air, and a crankshaft angle. A crank angle sensor 45 that outputs a corresponding signal is connected. In controlling the electric motor 12, a value obtained from a predetermined function formula or a map may be used instead of the value actually measured by these sensors. Further, an output signal of a position detection sensor built in the motor 12 is also input to the motor control device 40.
[0042]
Next, control of the motor 12 by the motor control device 40 will be described. In the following, control of the motor 12 for driving the intake valve 4 of one cylinder 2 will be described, but the same applies to control of the motor 12 for driving the other intake valve 4. The same applies to the motor 12 that drives the exhaust valve 5.
[0043]
FIG. 7 shows a motor drive control routine that is repeatedly executed at regular intervals by the motor control device 40 to change the output torque of the motor 12 according to the operating state of the internal combustion engine 1. By executing the motor drive control routine of FIG. 7, the motor control device 40 functions as a motor control unit. In this motor drive control routine, the motor control device 40 first detects the rotational position of the cam 21A based on, for example, the position detection sensor of the motor 12 and the reduction ratio of the gear train 15 in step S1. In step S1, the motor control device 40 functions as a cam position specifying unit.
[0044]
Next, in step S2, the operation state of the internal combustion engine 1 necessary for determining the operation content of the intake valve 4 is detected. For example, the rotation speed (rotation speed), load factor, and the like of the internal combustion engine 1 are detected based on the output signals of the sensors 41 to 45 described above. In the following step S3, the operation content of the intake valve 4 is determined based on the detection result of the operating state of the internal combustion engine 1. For example, parameters such as the amount of lift to be given to the intake valve 4, the phase of the camshaft 14 </ b> A, the number of revolutions, and the like are determined in accordance with the current operating state.
[0045]
In the following step S4, an estimated value TF of the cam friction torque is obtained by the following equation (1). The rotational resistance applied to the motor 12 based on the mechanical configuration from the motor gear 18 to the intake valve 4 or the exhaust valve 5 is referred to as a cam friction torque herein.
[0046]
(Equation 1)
TF (θ + θ3) = Tf + f1 (Tf1, θmax−θ1, θ + θ3) + f2 (Tf2, θmax + θ2, θ + θ3) (1)
Here, Tf is a base friction torque, f1 is a polynomial approximation function describing a fluctuation component of the cam friction torque generated by the push-back action of the cam 21A by the valve spring 23, and f2 is generated by the push-out action of the cam 21A by the valve spring 23. A polynomial approximation function describing a fluctuation component of cam friction torque, θ is a crank angle at the time of execution of control, and θ3 is a time constant determined according to the motor 12. Hereinafter, equation (1) will be described with reference to FIGS. 8 and 9.
[0047]
FIG. 8 shows a correspondence relationship between the crank angle θ, the valve lift (the lift amount of the intake valve 4), the cam friction torque TF (θ), and the drive current I (θ) of the motor 12. However, the cam friction TF indicates the forward direction, that is, the direction in which resistance to the rotation of the cam 21A is associated with the downward direction in FIG. FIG. 8 shows the cam friction torque TF and the drive current I of the motor 12 when the valve lift amount is changed in two levels. That is, the case where the valve lift is large is indicated by a thick line, and the case where the valve lift is large is indicated by a thin line.
[0048]
As is clear from FIG. 8, the base friction torque Tf of the first term of the equation (1) acts in the positive direction, and its value is constant irrespective of the crank angle θ. That is, the base friction torque Tf indicates a basic rotational resistance applied to the motor 12 when rotating the cam 21A. Next, a reference position is set at an appropriate position on the horizontal axis in FIG. 8, and the valve lift reaches its maximum value at a position where the crank angle θ advances by θmax from the reference position (hereinafter, this position is referred to as a maximum lift position). When the intake valve 4 is opened before reaching the maximum lift position θmax, the cam friction torque TF (θ) increases in the positive direction from the base friction torque Tf and shows a peak, while the intake valve 4 reaches the maximum lift position θmax. In the closing process, the torque decreases in the negative direction from the base friction torque Tf. Such a change in the friction torque TF (θ) is such that when the cam 21A opens the intake valve 4 against the valve spring 23, the repulsive force of the valve spring 23 pushes the cam 21A back in the direction opposite to the rotation direction. After the repulsive force of the valve spring 23 exceeds the peak, the repulsive force of the valve spring 23 acts to push the cam 21A in the rotational direction.
[0049]
Strictly, the variation of the cam friction torque TF corresponding to an arbitrary crank angle θ from the base friction torque Tf can be calculated mechanically or mechanically from the configuration of the valve driving device 11A. However, the correlation between the crank angle θ and the variation of the cam friction torque TF is such that the peak values Tf1 and Tf2 of the variation of the cam friction torque with respect to the base friction torque Tf and the crank angle at which the peak values Tf1 and Tf2 are given. The deviation of θ from the maximum lift position θmax can be approximately expressed by a function using variables θ1 and θ2 as variables. The second terms f1 and f2 in the above-described equation (1) are approximate functions obtained from such a viewpoint. Information specifying these approximate functions is recorded in the ROM of the motor control device 40.
[0050]
The maximum lift position θmax is determined in the process of step S3 in FIG. As shown in FIG. 9, there is a correlation between the maximum lift amount of the intake valve 4 and the base friction torque Tf, the peak values Tf1, Tf2, and the crank angle deviation amounts θ1, θ2. It is recorded in the ROM of the control device 40 in a map format. Accordingly, in the process of step S4, the motor control device 40 first obtains the base friction torque Tf, the peak values Tf1, Tf2, and the crank angle deviation amounts θ1, θ2 corresponding to the current maximum lift amount with reference to the map in the ROM. Then, these values and the current crank angle θ specified based on the output of the crank angle sensor 45 are substituted into the equation (1) to determine the cam friction torque TF. However, when these values are corrected in step S10 or S11 described later, the correction is reflected to determine the cam friction torque TF.
[0051]
However, if the motor 12 has a response delay and the response delay is given by a crank angle θ and a time constant θ3, when the crank angle θ leads the current crank angle θ by a time constant θ3. It is necessary to obtain the cam friction torque TF at this time. Therefore, in the second and third terms of the equation (1), a time constant θ3 is added to the crank angle θ. Note that, instead of the polynomial approximation functions f1 and f2, the fluctuation component of the cam friction torque may be obtained by a physical model.
[0052]
Returning to FIG. 7, the description will be continued. After the calculation of the cam friction torque TF, the process proceeds to step S5, in which the cam friction torque TF (θ + θ3) is multiplied by a predetermined gain α to obtain a drive current I (θ) of the motor 12 to be given at the present time. In the following step S6, the drive current I (θ) for the motor 12 is set and the drive of the motor 12 is executed. As is apparent from FIG. 8, the change in the cam friction torque TF (θ) is reflected earlier in the motor drive current I (θ) given in step S6 by the motor time constant θ3. Therefore, when the cam friction torque TF (θ) becomes larger than the base friction torque Tf (when it changes to the lower side in FIG. 8), the output torque of the motor 12 increases accordingly, and the cam friction torque TF (θ) ) Becomes smaller than the base friction torque Tf (when it changes to the upper side in FIG. 8), the output torque of the motor 12 also decreases accordingly. Thereby, the output torque of the motor 12 is controlled without excess or deficiency.
[0053]
After the drive of the motor 12 is performed, the process proceeds to step S7, and it is determined whether or not the difference between the current drive current I (θ) and the standard drive current I (θ) is within a predetermined threshold value λ. The standard drive current I (θ) is a drive current obtained without considering the correction in step S10 or step S11. If it is determined in step S7 that the value is within the threshold value λ, the process proceeds to step S8, in which a value obtained by subtracting the target air-fuel ratio (target A / F) from the air-fuel ratio (measured A / F) detected by the A / F sensor 41 is a predetermined threshold value. It is determined whether it is less than β. Here, the target A / F is a target value of the air-fuel ratio set according to the operating state of the internal combustion engine 1. Since the valve operating characteristics of the intake valve 4 are appropriately set according to the operating state of the internal combustion engine (see step S3), the target A / F is determined if the operating state of the intake valve 4 is properly controlled. It corresponds to the air-fuel ratio that would be obtained.
[0054]
When the measured A / F exceeds the target A / F by more than the threshold value β and the condition of step S8 is denied, that is, the actual air-fuel ratio deviates from the target air-fuel ratio to the rich side by more than the threshold value β. In step S10, at least one parameter of the crank angle deviations θ1 and θ2 and the peak values Tf1 and Tf2 of the cam friction torque variation to be substituted into the equation (1) is determined by using the map of FIG. It is decreased from the specified value by an amount corresponding to the difference in the air-fuel ratio. The decrease in the peak values Tf1 and Tf2 means that these values are changed so as to approach the base friction torque Tf. Due to such a change, the intake valve 4 is controlled to close relatively, that is, to reduce the lift amount. Therefore, in step S10, the deviation between the measured A / F and the target A / F is eliminated by reducing the lift amount of the intake valve 4 and relatively reducing the intake air amount.
[0055]
On the other hand, when the condition of step S8 is affirmed, the process proceeds to step S9, and it is determined whether or not a value obtained by subtracting the measured A / F from the target A / F is equal to or less than a predetermined threshold value γ. If the condition in step S9 is affirmed, the current motor drive control routine ends. On the other hand, if the measurement A / F is smaller than the target A / F by more than the threshold γ and the condition of step S9 is denied, that is, the actual air-fuel ratio is leaner than the threshold γ with respect to the target air-fuel ratio. If there is a large deviation, the process proceeds to step S11, and at least one of the parameters of the crank angle deviation amounts θ1 and θ2 and the peak values Tf1 and Tf2 of the cam friction torque fluctuation amount to be substituted into the equation (1) is set to the value shown in FIG. It is increased from the value specified by the map by an amount corresponding to the difference in the air-fuel ratio. The increase in the peak values Tf1 and Tf2 means that these values are changed so as to be away from the base friction torque Tf. Due to such a change, the intake valve 4 is controlled to open relatively, that is, to increase the lift amount. Therefore, in step S11, the deviation between the measured A / F and the target A / F is eliminated by increasing the lift amount of the intake valve 4 to relatively increase the intake air amount.
[0056]
After correcting the variables θ1, θ2, Tf1 or Tf2 in step S10 or S11, the process proceeds to step S12. In step S12, it is determined whether or not the amount of increase or decrease of the parameter is greater than a threshold value Ψ. If it is within the threshold Ψ, the process returns to step S4 to calculate the cam friction torque TF. At this time, for the variables θ1, θ2, Tf1, and Tf2 that have been corrected in step S10 or S11, the corrected values are used.
[0057]
On the other hand, if it is determined in step S12 that the amount of increase or decrease is greater than the threshold value Ψ, it is determined that the valve driving device 11A is abnormal, and the process proceeds to step S13 to issue a predetermined warning to notify the driver of the abnormality of the valve driving device 11A. I do. For example, a warning light on an instrument panel of a vehicle is turned on or blinks. Then, the process proceeds to step S15, where a predetermined evacuation traveling process is started, and the motor drive control routine ends. If the difference between the drive currents I (θ) exceeds the threshold value λ in step S7, it is determined that the motor 12 is abnormal, and the process proceeds to step S14 to issue a predetermined warning to notify the driver of the abnormality of the motor 12. . For example, a warning light on an instrument panel of a vehicle is turned on or blinks. Then, the process proceeds to step S15.
[0058]
According to the above embodiment, the output torque of the motor 12 is controlled without excess or deficiency in accordance with the increase or decrease of the cam friction torque, so that the variation in the rotation speed of the cam shaft 14A due to the influence of the fluctuation of the cam friction torque is suppressed. The operation characteristics of the cam 21A can be accurately controlled with respect to the target value. Therefore, the fuel efficiency and power performance of the internal combustion engine 1 are improved, and deterioration of exhaust emission is prevented.
[0059]
Further, since the deviation of the air-fuel ratio is specified and the output torque of the motor 12 is controlled so that the deviation is corrected, the deviation can be determined according to the actual state of the valve drive device 11A without depending only on the control target value. Thus, the output torque of the motor 12 can be appropriately controlled. For example, when the states of the valve driving device 11A are different from those at the time of setting the approximation functions f1 and f2 in FIG. 8 and the map in FIG. 9 due to individual differences and aging of the valve driving device 11A, the difference is different. Appears as a shift in air-fuel ratio. Therefore, if the drive current of the motor 12 is controlled so as to correct the deviation of the air-fuel ratio, as a result, the operating characteristics of the intake valve 4 can be appropriately controlled by correctly reflecting the state of the valve drive device 11A. Since the drive current of the motor 12 corrected in this way correctly reflects the lift amount and phase of the intake valve 4, the amount of intake air into the cylinder 2 is determined based on the corrected drive current of the motor 12. It can also be calculated correctly.
[0060]
Furthermore, according to the above-described embodiment, when the drive current of the motor 12 is set to be significantly larger or smaller than the standard drive current, it is determined that the motor 12 is abnormal (step S7 → S14), and the air-fuel ratio is determined. When the correction amount (increase / decrease amount) of the parameter corresponding to the deviation is larger than the allowable level, it is determined that the valve driving device is abnormal (step S12 → S13), thereby causing the motor control device 40 to function as abnormality determining means. ing. If the drive current of the motor 12 is excessively large or small compared to the standard drive current, it is highly possible that the motor 12 does not operate normally. Even if the drive current is normal, the deviation of the air-fuel ratio is eliminated. If the correction amount necessary for the above is excessively large in the positive direction or the negative direction, it is highly possible that an abnormality occurs in one of the valve driving devices 11A and the intake valve 4 is not correctly driven. An abnormality of the valve drive system 10 can be appropriately determined. As described above, since the abnormality of the motor 12 and the valve driving device 11A is determined based on the correction amount of the driving current of the motor 12, a sensor for monitoring the operation state of the valve driving device 11A needs to be separately provided for abnormality diagnosis. Cost can be prevented.
[0061]
The correction of the motor output torque in steps S8 to S11 and the determination of the presence / absence of abnormality in step S7 or S12 are not unique to the feedforward control of the motor output torque based on the estimation of the friction torque, but are performed in various controls related to the motor 12. May be performed in combination. For example, for the feedback control of the output torque of the motor 12 based on the rotation speed of the crankshaft, the correction of the output torque and the abnormality determination can be performed as in the example of FIG.
[0062]
In the above-described embodiment, it is desirable that the increase or decrease obtained in step S10 or S11 be stored in the storage device in the motor control device 40 as the correction amount of the friction torque TF. In this case, the storage device is desirably a backup RAM backed up by a battery of the vehicle, or a non-volatile memory such as a rewritable flash ROM that does not require a power supply for storing and storing. If such a storage device is used, the correction amount is held even after the ignition switch is turned off and the internal combustion engine 1 is stopped, and the cam is referenced by referring to the stored correction value from the next start of the internal combustion engine 1. The friction torque TF can be properly calculated.
[0063]
The above-described feedforward control of the motor output torque based on the prediction of the cam friction torque may be executed in parallel with other control relating to the motor output torque, or may be executed alone. For example, the feedback control of the cam angle based on the crank angle detected by the crank angle sensor 45 and the feedforward control of the cam friction torque described above may be performed in parallel.
[0064]
The valve drive system 10 of the present embodiment has several features in addition to the above-described basic configuration for controlling the operations of the intake valve 4 and the exhaust valve 5 according to the operating state of the internal combustion engine 1. . The description will be made in the following order. Note that various mechanisms or structures of the intake-side valve drive device 11A described below are also provided on the exhaust-side valve drive device 11B and have the same operational effects as those of the valve drive device 11A unless otherwise specified. It is.
[0065]
(Cam position detection)
In the valve drive system 10 of the present embodiment, the position of the cam 21A is specified by using the rotational position detecting means of the motor 12 (see step S1 in FIG. 7). Preferably, a magnetic pole sensor of one pole pair is used for the rotational position detecting means. The magnetic pole sensor has the same number of S poles and N poles around the output shaft, while the output shaft rotates in the order of S pole → N pole → S pole or N pole → S pole → N pole. It is configured to output a rotation signal of 0 ° to 360 °. In a normal motor, the number of magnetic poles of the magnetic pole sensor is adjusted to the number of magnetic poles of the motor 12. For example, if the motor 12 is a 4-pole pair (a pair of S pole and N pole), the magnetic pole sensor is a 4-pole pair, and if the motor 12 is an 8-pole pair, an 8-pole magnetic pole sensor is used. However, in the present embodiment, a single pole pair magnetic pole sensor is used as the position detection sensor of the motor 12 irrespective of the number of poles of the motor 12. In this case, since the rotation position of the output shaft of the motor 12 and the output signal of the position detection sensor correspond to 1: 1, there is an advantage that the rotation position of the motor 12 can be easily determined. In particular, when the speed ratio between the motor 12 and the camshaft 14A is 1: 1, the rotational position of the motor 12 and the rotational position of the cam 21A correspond to 1: 1. It is convenient to represent the rotational position of 21A.
[0066]
On the other hand, if the reduction ratio from the motor 12 to the camshaft 14A cannot be set to 1: 1 due to the gear train 15 or the like, it is unambiguously determined to which rotation position of the cam 21A the rotation position of the motor 12 corresponds. Since it cannot be determined, the rotational position of the cam 21A cannot be controlled unless an initialization operation for specifying the correspondence between the two is performed. The initialization operation can be performed by actually driving the cam 21A and detecting which rotation position of the motor 12 corresponds to the predetermined cam angle. However, the speed reduction ratio from the motor 12 to the cam 21A can be reduced. When N: M (where N> M and N and M are integers having no common divisor other than 1), the rotational position of the motor 12 corresponding to a specific cam angle among the cam angles 0 to 360 ° (motor Angles) exist at N positions between the cam angles 0 to 360 °, that is, every 360 / N °. For example, when the reduction ratio is set to N: M = 5: 3 as shown in FIG. 10, the cam 21A makes three rotations while the motor 12 makes five rotations. Any one of the five positions (shown by black circles in the figure) corresponds to the cam angle of 0 °. Therefore, the smaller N is, the easier it is to detect the cam position. In view of the margin for erroneous detection, if the motor angle corresponding to the specific cam angle is set at every 60 ° or at each angle larger than N, a preferable range of N is 6 or less.
[0067]
(About cam initialization)
Next, an initialization operation regarding the cam position will be described. FIG. 11 shows a cam position initialization routine executed by the motor control device 40 to initialize the cam position. By executing the cam position initialization routine shown in FIG. 11, the motor control device 40 functions as initialization means. In this routine, the motor control device 40 first starts the motor 12 in step S21 to rotate the cam 21A. At this time, the rotation speed of the motor 12 is fed back using a position signal or the like from the rotation position sensor, and the output torque of the motor 12 is controlled so that the rotation speed becomes constant. The output torque is controlled by increasing or decreasing the drive current. In the following step S22, a cam friction torque is detected using the drive current that has been subjected to the feedback control. In the next step S23, it is determined whether or not the motor 12 has rotated by one rotation of the cam 21A, and if not completed, the process returns to step S22. If the cam 21A has made one rotation, the cam is stopped in step S24 and the process proceeds to step S25.
[0068]
In step S25, the correspondence between the position of the cam 21A and the rotation position of the motor 12 is specified based on the detection result of the cam friction torque. That is, if the motor speed is constant as shown in FIG. 12A, there is a correlation between the cam friction torque and the motor output torque, and the cam friction torque starts from the position Pa at which the cam 21A starts to open the intake valve 4. Increases, the output torque also increases, and the cam friction torque and the motor output torque are reversed at a position Pb at which the nose portion 21a of the cam 21A reaches an extension of the intake valve 4, the intake valve 4 is completely closed, and the cam 21A is closed. At the separated position Pc, the cam friction torque and the motor output torque converge to their respective base values. However, although there is actually an effect of the motor time constant as shown in FIG. 8, the time constant of the motor 12 is ignored in FIG.
[0069]
By utilizing such a relationship between the cam friction torque and the motor output torque, at least one of the cam positions Pa, Pb, and Pc is determined, and the correspondence between the determined position and the rotation position of the motor 12 is determined. Can be grasped. Then, using this correspondence, the current cam position (cam angle) is specified in step S25 in FIG. In a succeeding step S26, information on the cam position specified by the initialization operation is stored, and thereafter, the initialization operation routine ends.
[0070]
According to the above processing, since the cam position can be specified from the change in the motor output torque, there is an advantage that it is not necessary to separately provide a sensor for detecting the cam position. However, the present invention is not limited to specifying the cam position based on the motor output torque. For example, as shown in FIG. 12B, when the cam 21A is rotated while the motor output torque is kept constant, the rotation speed of the motor 12 fluctuates according to the cam friction torque. Therefore, the motor speed or acceleration may be obtained by using a signal from the rotation position sensor of the motor 12, and the cam position may be specified from the change in the speed or acceleration. In any case, the cam position can be specified by monitoring various physical quantities having a correlation with the change in the cam friction torque.
[0071]
The above-described cam position initialization routine can be performed when the internal combustion engine 1 is started or stopped. Specifically, when the ignition switch is turned on, a cam position initialization routine is executed prior to the cranking operation, or when the ignition switch is turned off and the stop of the internal combustion engine 1 is confirmed, the motor control is performed. Prior to the interruption of the power supply to the device 40, a cam position initialization routine is executed. When the initialization is performed when the ignition switch is turned on, the obtained information on the cam position may be stored in various storage devices as long as the motor control device 40 can refer to the information. On the other hand, when initialization is performed when the ignition switch is turned off, the obtained cam position information is stored in a backup RAM backed up by a vehicle battery, or a rewritable flash that does not require a power supply for storing and storing data. It is stored in a non-volatile memory such as a ROM. If such a storage device is used, initialization is unnecessary at the time of starting the internal combustion engine 1, and control of the cam 21A can be immediately started using the stored cam position.
[0072]
Further, the execution timing of the cam position initialization routine is not limited to immediately after the turning on or off of the ignition switch, and may be performed as needed as long as it does not affect the operation of the internal combustion engine 1. For example, the cam position initialization routine may be executed during idling stop, or during the so-called reduced cylinder operation in which combustion is stopped in some cylinders for deceleration or the like, the stopped cylinder (combustion stopped) The cam initialization routine may be executed with respect to the cam 21A corresponding to the cylinder 21A.
[0073]
(About power generation using cam rotation)
In FIG. 8 described above, the cam friction torque TF (θ) is always greater than 0, and the drive current is supplied to the motor 12 through one rotation of the cam 21A. However, depending on the magnitude of the force of the valve spring 23 pushing the cam 21A and the base friction torque Tf, the cam friction torque TF becomes negative as shown in FIG. May be rotationally driven. When such a state occurs, a motor (also referred to as a motor generator) 12 generates power as shown in FIG. 14, and the obtained power is charged into the battery 51 via the inverter circuit 50. Thus, an appropriate load may be applied to the rotation of the cam 21A.
[0074]
[Second embodiment]
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the output torque of the motor 12 is controlled by estimating the cam friction torque. In this embodiment, however, the change in the rotation speed (rotation speed) of the internal combustion engine 1 based on the operating state of the internal combustion engine 1 is performed. And the output torque of the motor 12 is controlled in accordance with the result of the prediction. Note that the mechanical configuration of the valve driving devices 11A and 11B is the same as that of the first embodiment.
[0075]
FIG. 15 is a block diagram of a control system mounted on the motor control device 40 according to the second embodiment of the present invention. This configuration may be realized by a combination of a CPU and software, or may be realized by a hardware circuit. In this embodiment, the required cam angle as a control target value is calculated based on the crank angle detected by the crank angle sensor 45 and the valve timing (required valve timing) required according to the operating state of the internal combustion engine 1. You. A deviation between the required cam angle and an actual cam angle (actual cam angle) given as input information is obtained, and the output torque of the motor 12 is PID-controlled based on the deviation.
[0076]
Further, in the control system of FIG. 15, some parameters related to the change in the rotation speed of the internal combustion engine 1 (for example, the accelerator opening, the intake air amount, the fuel injection amount) are monitored. The correction amount of the output torque corresponding to these parameters is obtained using a predetermined map. When the vehicle is provided with an automatic transmission, the shift position may be monitored as a parameter. The shift position can be obtained by referring to a shift diagram of the transmission. The correspondence between each parameter and the correction amount may be obtained by a bench conformity test or computer simulation.
[0077]
Then, a value obtained by adding the correction amount of the output torque obtained based on the map to the output torque obtained by the PID control is output as the required torque. The motor control device 40 controls the drive current of the motor 12 based on the required torque.
[0078]
In the above embodiment, the change in the rotational speed of the internal combustion engine 1 is indirectly predicted via the accelerator opening and the like, and a correction amount of the motor output torque is given from a map according to the predicted result. As a result, the output torque of the motor 12 is subjected to feedforward control. Accordingly, the responsiveness of the driving speed of the cam to the change in the rotation speed of the internal combustion engine 1 can be improved.
[0079]
FIG. 16 illustrates an example of feedforward control of cam output torque when a change in the number of revolutions is predicted based on the accelerator opening. Note that the feedforward torque in the drawing means a correction amount of the output torque specified from the map in the control system of FIG. 15, and is not the required torque itself. In the example of FIG. 16, the feedforward torque is increased by a predetermined amount for a fixed period A in response to a rapid increase in the accelerator opening. Although the rotation speed of the internal combustion engine 1 increases with an increase in the accelerator opening, if the feedforward torque is not applied, the required cam angle shown by the solid line in FIG. Is delayed. For example, if only the output torque of the motor 12 is feedback-controlled based on the rotation speed of the internal combustion engine 1, such a cam angle shift may occur. However, when the feedforward torque is applied, the required cam angle and the actual cam angle can be substantially matched to improve the responsiveness of the cam.
[0080]
FIG. 17 shows an example of feedforward control of the cam output torque when a change in the number of revolutions is predicted based on the shift position. In this example, when a downshift request is given based on a shift diagram of the transmission, the feedforward torque is increased by a predetermined amount for a certain period B in response to the request. Although the rotation speed of the internal combustion engine 1 is increased by executing the downshift, if the feedforward torque is not applied, the required cam angle shown by the solid line in FIG. Response delay occurs. However, when the feedforward torque is applied, the required cam angle and the actual cam angle can be made substantially coincident with each other even during downshifting, so that the responsiveness of the cam can be improved.
[0081]
In addition to the above, the change in the rotation speed may be predicted with reference to various parameters correlated with the change in the rotation speed of the internal combustion engine 1. Note that the feedforward control of the motor output torque based on the prediction of the change in the rotation speed may be executed in parallel with other control relating to the motor output torque, or may be executed alone. For example, at least one of the feedback control of the cam angle based on the crank angle detected by the crank angle sensor 45 and the feed forward control based on the prediction of the cam friction torque in the first embodiment, and the feed in the second embodiment The forward control may be performed in parallel.
[0082]
[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the present embodiment, the drive mode of the motor 12 of each of the valve drive devices 11A and 11B is switched between a forward rotation mode and a forward / reverse rotation mode according to the operation state of the internal combustion engine 1. The forward rotation mode is a mode in which the motor 12 is continuously rotated in a fixed direction (forward rotation direction), and the forward / reverse rotation mode is a mode in which the rotation direction of the motor 12 is appropriately switched between the forward rotation direction and the reverse rotation direction. is there. The mechanical configuration of the valve driving devices 11A and 11B is the same as in the first embodiment.
[0083]
FIG. 18 shows an example of a switching condition regarding the drive mode of the motor 12. In this example, the motor drive mode is switched based on the rotation speed and load of the internal combustion engine 1, and the forward rotation mode is applied at a high rotation and high load, and the forward and reverse rotation mode is applied at a low rotation and low load. In the forward / reverse rotation mode, the rotation direction of the motor 12 is switched at an arbitrary position while the intake valve 4 or the exhaust valve 5 is being opened, so that the cams 21A and 21B are at the maximum lift position, that is, the intake valve 4 or the exhaust valve 5 is at the maximum lift position. The intake valve 4 or the exhaust valve 5 can be closed before reaching the position where the quantity is given.
[0084]
That is, as shown in FIG. 19, when the maximum lift amount when the motor 12 is rotated in the normal rotation mode is La, the motor 12 is temporarily stopped before the cams 21A and 21B reach the maximum lift position θmax in the normal and reverse rotation mode. When the rotation is stopped and then reversed, the maximum lift amount of the intake valve 4 and the exhaust valve 5 can be limited to a smaller Lb. As a result, an excessive increase in the amount of intake air can be prevented. Further, by selecting the forward / reverse rotation mode at the time of starting, a decompression function (a function of opening the intake valve 4 or the exhaust valve 5 to reduce the compression pressure) with excellent responsiveness can be realized. On the other hand, if the normal rotation mode is applied during high-load high-speed rotation, the cams 21A and 21B can be rotated at a high speed with a relatively small torque by using the inertia of the cams 21A and 21B and the gear train 15 and the like.
[0085]
Note that the lift amount Lb in the forward / reverse rotation mode may be appropriately changed according to the operating state of the internal combustion engine 1. In order to make the lift amount Lb variable, the rotation angle of the cam 21A may be increased or decreased by the motor control device 40 according to the lift amount Lb.
[0086]
FIG. 20 shows a drive mode determination routine that the motor control device 40 repeatedly executes at an appropriate cycle during operation of the internal combustion engine 1 to switch the drive mode of the motor 12. When the motor control device 40 executes the drive mode determination routine, the motor control device 40 functions as a lift amount control unit and a mode switching unit.
[0087]
In the drive mode determination routine of FIG. 20, the motor control device 40 acquires the rotation speed and load of the internal combustion engine 1 in step S31, and in step S32, the current operating state of the internal combustion engine 1 is correct according to the conditions shown in FIG. It is determined whether or not it is in the area for selecting the transfer mode. Then, the normal rotation mode or the normal / reverse rotation mode is selected according to the determination result (step S33 or S34), and thereafter, the drive mode determination routine ends.
[0088]
In determining the drive mode, not only the engine speed and the engine load but also various parameters correlated with the operating state of the internal combustion engine 1 may be referred to. Further, the switching condition between the forward rotation mode and the forward / reverse rotation mode is not limited to the example of FIG. 18 and may be appropriately changed. The control of the output torque of the motor 12 in the forward rotation mode can use the feedforward control of the first and second embodiments described above.
[0089]
[Fourth embodiment]
Next, a fourth embodiment of the present invention will be described. In the present embodiment, the motor control device 40 is caused to function as valve rotation execution means by causing the motor control device 40 to execute the cleaning control routine of FIG. 21 at a predetermined time while the internal combustion engine 1 is stopped. Note that the mechanical configuration of the valve driving devices 11A and 11B is the same as that of the first embodiment.
[0090]
In the cleaning control routine of FIG. 21, the motor control device 40 starts the high-speed rotation of the motor 12 in step S41, and determines in step S42 whether a predetermined time has elapsed from the start of rotation of the motor 12. When the predetermined time has elapsed, the process proceeds to step S43, and the motor 12 is stopped.
[0091]
As described above, when the motor 12 is rotated at high speed while the internal combustion engine 1 is stopped, the intake valve 4 opens and closes at high speed as shown in FIG. The load is reduced, and the intake valve 4 rotates around the axis of the stem 4a. As a result, carbon attached between the intake valve 4 and the valve seat 60 is removed. Further, with the rotation of the intake valve 4, the contact portion of the stem upper end 4b with the rocker arm 16 is displaced in the circumferential direction, so that the stem upper end 4b is substantially displaced in the circumferential direction as shown by the hatched area in FIG. Becomes uniform wear. Incidentally, if the stem 4a does not rotate, only a specific portion of the stem upper end 4b comes into contact with the rocker arm 16, and uneven wear of the stem upper end 4b occurs as shown by a hatched area in FIG. 23 (b). Although the case of the intake valve 4 has been described above as an example, the cleaning control routine of FIG. 21 is similarly executed for the exhaust valve 5.
[0092]
The execution timing of the cleaning control routine in FIG. 21 is preferably such that a long-term stoppage of the internal combustion engine 1 can be expected, for example, by removing an ignition key. However, it is not necessary to execute the cleaning control routine of FIG. 21 every time the internal combustion engine 1 is stopped, and the state of carbon deposition on the intake valve 4 and the exhaust valve 5 and the progress of wear of the stems of the intake valve 4 and the exhaust valve 5. The execution time may be appropriately determined according to the conditions.
[0093]
【The invention's effect】
As described above, according to the valve drive system of the present invention, by providing a plurality of valve drive devices, each of the intake valves or the exhaust valves of the plurality of cylinders is adapted to the operation state of the internal combustion engine. Appropriate operating characteristics can be provided. In particular, when at least one of the operating angle of the intake valve or the exhaust valve, the lift characteristic, or the maximum lift amount is changed by the operation control of the electric motor, a conventional valve driving device that changes only the opening / closing timing is provided. In comparison, the operations of the intake valve and the exhaust valve can be changed more flexibly.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a main part of a valve drive system according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing a configuration of a valve driving device provided corresponding to one cylinder.
FIG. 3 is a perspective view of the valve drive device from another direction.
FIG. 4 is a perspective view of the valve driving device from still another direction.
FIG. 5 is a perspective view of a valve characteristic adjusting mechanism.
FIG. 6 is a perspective view showing a valve characteristic adjusting mechanism partially cut away.
FIG. 7 is a flowchart illustrating a procedure of a motor drive control routine executed by the control device of FIG. 2;
FIG. 8 is a diagram illustrating an example of a relationship between a crank angle, a valve lift, a cam friction torque, and a motor drive current.
FIG. 9 is a diagram showing an example of a correspondence relationship between a maximum lift amount of a valve, a crank angle, and a cam friction torque.
FIG. 10 is a diagram illustrating an example of a correspondence relationship between a cam angle and a motor angle.
FIG. 11 is a flowchart showing the procedure of a cam position initialization routine executed by the control device of FIG. 2;
FIG. 12 is a diagram illustrating an example of a correlation among a motor speed, a cam friction torque, and a motor output torque.
FIG. 13 is a diagram showing an example in which cam friction torque is negative.
FIG. 14 is a diagram showing a configuration for performing regenerative power generation by a cam driving motor.
FIG. 15 is a block diagram of a control system for predicting a change in the rotation speed of the internal combustion engine and controlling the output torque of the motor in the second embodiment of the present invention.
FIG. 16 is a diagram showing an example of control realized by the control system of FIG.
FIG. 17 is a diagram showing another example of control realized by the control system of FIG.
FIG. 18 is a diagram showing conditions for switching a drive mode of a motor between a forward rotation mode and a forward / reverse rotation mode in a third embodiment of the present invention. .
FIG. 19 is a diagram showing a correspondence relationship between a crank angle, a valve lift, and a motor speed in each of a forward rotation mode and a forward / reverse rotation mode.
FIG. 20 is a diagram showing a drive mode determination routine executed by the control device for setting a drive mode.
FIG. 21 is a flowchart showing a procedure of a cleaning control routine executed by the control device to perform cleaning of the intake valve or the exhaust valve.
FIG. 22 is a diagram illustrating a state in which cleaning is performed by operating an intake valve at a high speed.
FIG. 23 is a diagram showing a comparison between the state of wear of the upper end portion of the stem when cleaning control is performed (a) and the case where cleaning control is not performed (b).
[Explanation of symbols]
1 Internal combustion engine
2 cylinder (cylinder)
4 Intake valve
5 Exhaust valve
10 Valve drive system
11A, 11B Valve drive device
12 Electric motor
13 Power transmission mechanism
15 Gear train
21A, 21B Cam
23 Valve spring
40 motor control device (motor control means, abnormality determination means, cam position specification means, initialization means, valve rotation execution means, lift amount restriction means, mode switching means)

Claims (17)

A valve drive system for an internal combustion engine, which is applied to an internal combustion engine having a plurality of cylinders and drives intake or exhaust valves provided in each cylinder, wherein the valves of different cylinders of the internal combustion engine are provided. A plurality of valves each provided with an electric motor as a drive source for generating a rotational motion and a power transmission mechanism for converting the rotational motion of the electric motor into an opening and closing motion of a valve to be driven and transmitting the electric motor; A driving device;
Motor control means for controlling the operation of the electric motor of each of the plurality of valve drive devices according to the operating state of the internal combustion engine,
A valve drive system for an internal combustion engine, comprising: The motor control means controls the operation of the electric motor in accordance with an operation state of the internal combustion engine so that at least one of the operating characteristics of the valve to be driven, a lift characteristic, and a maximum lift amount changes. The valve drive system according to claim 1, wherein the valve drive system controls the valve drive system. 3. The valve drive system according to claim 1, wherein the power transmission mechanism converts a rotational motion of the electric motor into the opening / closing motion using a cam. 4. 4. The valve drive system according to claim 3, wherein the motor control unit sets the control amount of the electric motor in consideration of a change in friction torque acting on rotation of the cam. 5. 5. The valve drive system according to claim 3, wherein the motor control unit sets a control amount of the electric motor in consideration of a control state related to intake or exhaust characteristics of the internal combustion engine. 6. The motor control unit is configured to correct a control amount of the motor such that the air-fuel ratio is controlled to a predetermined target value in consideration of a control state regarding an air-fuel ratio as the characteristic of the internal combustion engine. The valve drive system according to claim 5. An abnormality determining unit that determines whether there is an abnormality in the valve drive system based on a correction amount for the control amount of the electric motor given by considering a control state related to characteristics of intake or exhaust of the internal combustion engine. The valve drive system according to claim 5 or 6, wherein The motor control means predicts a change in the rotation speed of the internal combustion engine based on a change in an operation state of the internal combustion engine, and sets a control amount of the electric motor in consideration of the prediction result. The valve drive system according to claim 3. 4. The method according to claim 3, wherein when the friction torque acting on the rotation of the cam becomes a negative value, the electric motor is driven by the rotation of the cam to generate electric power by the electric motor. 5. 9. The valve drive system according to any one of items 8 to 8. Motor rotation position detection means for detecting a rotation position of the electric motor is attached to the electric motor, and the motor control means determines a rotation position of the cam based on a detection result of the rotation position of the electric motor. The valve drive system according to any one of claims 3 to 9, further comprising a specifying unit. When the reduction ratio between the electric motor and the cam is N: M (where N> M, and N and M are integers having no common divisor other than 1, N is set to 6 or less. The valve drive system according to claim 10, wherein: The motor control means rotates the electric motor according to predetermined conditions when the internal combustion engine is in a predetermined state, and drives the electric motor which appears during the rotation in correlation with a change in friction torque of the cam. The valve drive system according to any one of claims 3 to 11, further comprising initialization means for grasping a rotation position of the cam based on a change in a state. The initialization means is configured to rotate the electric motor when the internal combustion engine is stopped to determine the rotational position of the cam, and to store information indicating the determined rotational position of the cam even during the stop period of the internal combustion engine. The motor control means specifies the rotational position of the cam based on the information stored in the storage device and starts control of the electric motor at the next start of the internal combustion engine. The valve driving system according to claim 12, wherein 4. The motor control device according to claim 3, wherein the motor control unit includes a valve rotation execution unit that drives the electric motor such that the valve rotates around its axis at a predetermined time during the stop of the internal combustion engine. The valve drive system as described. The motor control means controls the amount of lift of the electric motor so that the amount of lift of the valve is limited to a predetermined value smaller than the maximum amount of lift obtained when the cam is rotated once. 4. A valve drive system according to claim 3, comprising means. The motor control means, the drive mode of the electric motor according to the operating state of the internal combustion engine, a forward rotation mode to drive the electric motor only in the forward direction, a forward and reverse rotation mode to rotate the electric motor forward and reverse The valve drive system according to claim 3, further comprising a mode switching unit that switches between the two modes. An electric motor as a drive source for generating rotational motion,
A power transmission mechanism that converts the rotational motion of the electric motor into an opening and closing motion of a valve to be driven and transmits the power;
Motor control means for controlling the operation of the electric motor such that at least one operating characteristic of a valve operating angle, a lift characteristic, or a maximum lift amount of the valve to be driven changes according to an operation state of the internal combustion engine. ,
A valve drive device for an internal combustion engine, comprising:

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